Caption "Scene on Rooipoort, de Beers farm on the Vaal River, Kimberley. April 1959.”

Acacia senegal and Acacia seyal are important agroforestry cash crops indigenous to several countries of sub-Saharan Africa, including Nigeria. The gum exudate produced by these species is termed gum Arabic which is an approved food additive (E414), primarily used as an emulsifier. In the current study, the molecular structure, composition and biophysical properties of gum samples harvested from mature trees of Acacia senegal at two specific ecolocations in Nigeria (NG1 and NG2), have been investigated together with two previously characterised gum samples harvested from A. senegal and A. seyal originating from Sudan. The monosaccharide sugar composition analyses have shown that the A. seyal gum had a lower rhamnose and glucuronic acid content than the A. senegal gum, but had higher arabinose content. No significant difference was observed between the sugar composition of the A. senegal gums from Sudan and Nigeria. The total protein content of the Nigerian gum samples were significantly higher than recorded for the Sudanese samples. The principal amino acids present in all the gum samples are hydroxyproline, serine, aspartame, threonine and proline which is in agreement with literature values. The hydrodynamic size of the molecules present in the gums was studied using dynamic light scattering and it was found that molecular association occurred in solution over time which was inhibited in the presence of an electrolyte. The comparison of droplet size distribution for emulsions prepared with A. senegal (NG1) and A. seyal gum samples showed that A. senegal sample was a better emulsifier than the A. seyal. Multilayer adsorption of the samples onto polystyrene latex particles was observed, which resulted in an increase in thickness of the adsorbed layer as a consequence of the interaction between the protein and carbohydrate within the molecules adsorbed on the emulsion surface. Preliminary analyses of the gums using transmission electron microscopy showed the presence of varied macromolecules, ranging in size from ~12 - ~60 nm. Immuno-gold negative staining (using JIM8 monoclonal antibody) indicated clear labelling of arabinogalactan-proteins present in the gums harvested from A. senegal, the labelling of the A. seyal sample was inconclusive. In summary, the data presented represents the first detailed comparison of the structure, composition and physicochemical characteristics of Nigerian Acacia gum exudates versus Sudanese samples (main global supplier) which have shown that gum obtained from Nigerian sources is a viable alternative to ensure future supply of this valuable natural resource.

Acacia mangium Willd. est une légumineuse ligneuse introduite dans de nombreux pays tropicaux à partir de son aire d'origine (Australie), avec ou sans inoculations volontaires par des rhizobiums sélectionnés. Des campagnes d'échantillonnage des bactéries symbiotiques fixatrices d'azote ont été réalisées dans sa zone d'origine à différentes époques (1986, 2007 et 2009) et dans trois zones d'introduction (Brésil, Sénégal et Malaisie). Après isolement et test de nodulation homologue, la diversité de plus de 500 souches a été analysée sur un gène de ménage (recA) et un gène symbiotique (nodA). Nous avons confirmé qu'A. mangium était essentiellement nodulé par des Bradyrhizobium. La comparaison des communautés symbiotiques issues de la zone d'origine et des zones d'introduction montre une importante diversité dans la région d'origine et une diversité plus réduite dans les zones d'introduction. En Australie, quelques génotypes sont majoritaires et persistent durant 20 ans. Une structuration phylogéographique et un isolement par la distance à une échelle mondiale ont été mis en évidence pour le gène symbiotique nodA. Enfin, lorsque A. mangium a été introduit conjointement avec une souche sélectionnée, le devenir de cet inoculum est variable en fonction des essais d'introduction. De plus, nous mettons en évidence des phénomènes de transfert du gène symbiotique nodA entre une souche introduite et les bactéries autochtones. Les résultats acquis nous permettent d'émettre des recommandations en termes de sauvegarde de la biodiversité microbienne symbiotique en zone naturelle, et sur la pertinence de procéder à des inoculations lors de la mise en place de plantations d'A. mangium. / From Australia, its native area and since three decades, the legume tree Acacia mangium Willd. has been introduced in many tropical countries, sometimes with selected rhizobium strains. A. mangium symbiotic nodule bacteria have been sampled in Australia at different times (1986, 2007, 2009), as well as in countries where it was introduced for inoculation trials (Brazil, Senegal and Malaysia). More than 500 isolates were obtained and checked for homologous nodulation. They were then characterized on the housekeeping recA and symbiotic nodA genes. We demonstrated through this study that A. mangium was almost always nodulated by Bradyrhizobium. Phylogenies of the obtained sequences were made, showing a high level of bacterial diversity in the native area, and a much more reduced diversity in introduced areas. In Australia, some genotypes were predominant and persist over 20 years. A phylogeographic structuration and isolation by distance at a global scale were demonstrated for the nodA symbiotic gene. Among introduced areas, the main result was the unsystematic occurrence of inoculated strains. We highlighted horizontal nodA symbiotic gene transfer between inoculated and indigenous bacterial strains. These data allow to make recommendations in terms of microbial diversity conservation in natural areas and on the need for inoculation of A. mangium in forestry practices.

Research into the micropropagation of black wattle in South Africa is important for two reasons. Firstly micropropagation technology allows breeders to select and propagate mature tissue, which in turn allows them to better capture selected traits. Secondly, tissue culture may control the highly invasive nature of black wattle. If triploid black wattle can be developed, foresters will then have to rely on clonal propagation to supply material for their growing operations. This research was part of the Institute for Commercial Forestry’s Acacia mearnsii vegetative propagation programme. The main focus of this research was to overcome various problems associated with direct organogenesis of ex vitro material. The shoot apex region was used as the explant in all studies because this region is thought to harbour relatively few internal microbial contaminants and is of sufficient size to withstand stresses associated with micropropagation. The initial research was focussed on the screening of sterilants, searching for a viable alternative to mercuric chloride. Surface sterilisation is integral to any micropropagation technique. This process should do the least amount of plant damage, whilst reducing microbial contamination to an acceptable level. Explants were cultured on Murashige and Skoog (MS) medium supplemented with 2.0 mg L-1 BA and monitored for signs of contamination and shooting. Household bleach proved an excellent alternative to mercuric chloride because it did significantly less damage to the explants than mercuric chloride and is handled easily. There was no significant effect of sterilant exposure time on explant decontamination levels, whilst the shortest exposure time resulted in significantly higher levels of shoot development than the other two times tested. The results of this initial research was developed into a protocol and utilised in subsequent investigations. Due to a considerable variation in the success of the developed surface sterilisation protocol according to different times of the year, a further investigation into the effects of season and mother plant material on shoot apex culture of Acacia mearnsii was undertaken. The success of any tissue culture technique depends on a large array of ex vitro and in vitro variables. The objective of this research was to determine the ii effect of two ex vitro variables, season and mother plant, on shoot apex culture of Acacia mearnsii. Explants from individual mother plants were cultured on MS medium supplemented with 2.0 mg L-1 BA during four separate seasons and monitored for signs of contamination and shooting. Spring was found to be the best harvesting season because spring explants showed significantly higher decontaminated explant levels and shooting levels than explants harvested in the other three seasons. The effect of mother plant selection on the performance of Acacia mearnsii explants during shoot apex culture was also found to be significant, especially with regard to shooting levels. Finally factors influencing shoot elongation of A. mearnsii during shoot apex culture were investigated. In the past, induction of shoot elongation during micropropagation of A. mearnsii was attained through the addition of plant growth regulators and other supplements to the basal culture medium. However, some micropropagation methods in other species have utilised red light as a means of promoting shoot elongation. The objective of this study was to test the effects of an alternative basal medium, red light and differing concentrations of chemical additions to the culture medium on shoot elongation of Acacia mearnsii during shoot apex culture. Four independent experiments were undertaken comparing: shoot elongation on Woody Plant Medium (WPM) to the MS basal medium control; shoot elongation under a red cellophane box compared to control culture light conditions; shoot elongation on media supplemented with various concentrations of GA3 to the un-supplemented control and shoot elongation on media supplemented with combinations of BA and IBA compared to a control. Although no significant effects were observed, many trends were noted. The results indicated that there was no advantage to using WPM instead of MS medium when attempting to elongate shoots, rejuvenated through shoot apex culture of A. mearnsii, whilst the effect of GA3 showed a negative trend. The effects of red light and some BA and IBA combinations showed positive trends on the elongation of initiated shoots. This research successfully addressed some of the problems associated with micropropagation of A. mearnsii. Shoot apex culture shows promise and further research into this technique should be considered. A viable surface sterilant alternative to mercuric chloride was successfully identified. This alternative is not only iii safer to use but shows a large reduction in phytotoxic effects. The effects of season and mother plant on shoot apex culture was successfully investigated, resulting in a better understanding of mother plant influences on tissue culture as well as the identification of an optimum season for explant selection. Finally two possible shoot elongation promoters were identified for further research and a more affordable alternative to red light sources and screens was identified. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

Made available in DSpace on 2015-04-01T14:16:04Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2775324 bytes, checksum: ce5694da4c072e08c6fa70d415e06035 (MD5) Previous issue date: 2013-02-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Lectins are proteins or glycoproteins of non-immune origin that have at least one non-catalytic site which binds reversibly to carbohydrates and glycoconjugates, which makes them ideal models for studies of cell-cell interactions and cell-virus, being good models for the design of new drugs. Some carbohydrate-binding proteins resembling the lectins but with some structural and functional differences, that exclude of this group. The Fabaceae Acacia farnesiana has in its seeds an agglutinin chitin-binding (AFAL), classified as PHA-like1. Its standard chromatographic revealed time-dependent oligomerization. This dynamic behavior complicates the protein crystallization and determining of the three dimensional structure. To better understand the structure-function relationship, this study aimed to examine AFAL anti-inflammatory activity through structural comparison with legume lectins. For both, it was the molecular modeling and docking with a glycan and carrageenan. AFAL model is folded as a β sandwich, which differs from the template used (Pisum sativum lectin) in loop regions, number of β-sheets and carbohydrate site. The docking showed that the protein binds to the carrageenan and glycan at different sites, which can be explained by absence of the sixth β-sheet (frontal β-sheets) and two β-sheets in posterior region. The A. farnesiana agglutinin can inhibit carrageenan induced inflammation due binding it, preventing its entrance into the cell and triggers the inflammatory process reactions. / Lectinas são proteínas e/ou glicoproteínas de origem não imune que possuem, no mínimo, um sítio não-catalítico que se liga de forma reversível a carboidratos e glicoconjugados, o que as tornam modelos ideais de estudos de interações célula-célula, célula-vírus, sendo bons modelos para o desenho de novos fármacos. Algumas proteínas possuem capacidade de se ligar a carboidratos, assemelhando-se às lectinas, porém com algumas diferenças estruturais e funcionais, que as excluem desse grupo. A Fabaceae Acacia farnesiana possui em suas sementes uma aglutinina ligante de quitina (AFAL), classificada como PHA-like1. Seu padrão cromatográfico revelou oligomerização tempo-dependente. Esse comportamento dinâmico dificulta a cristalização dessa proteína, bem como determinação da estrutura tridimensional. Visando compreender melhor a relação estrutura-função, este trabalho teve por objetivo analisar a atividade anti-inflamatória de AFAL através de comparação estrutural com lectinas de leguminosas. Para tanto, fez-se a modelagem e docking molecular com um glicano e a carragenina. A AFAL apresentou um modelo dobrado como um sanduiche de folhas β, que difere do molde utilizado (lectina de Pisum sativum) em regiões de loops, no número de folhas β e no sítio de ligação à carboidratos. O docking revelou que a proteína se liga à carragenina e ao glicano em sítios diferentes, o que pode ser explicado pela ausência de uma sexta folha β frontal e de duas folhas β na região posterior. A aglutinina de A. farnesiana pode inibir a inflamação causada por carragenina, por se ligar a ela, impedindo sua entrada na célula e o desencadeamento de reações típicas do processo inflamatório.

Cette étude concerne l’évaluation d’un essai de 46 provenances d’Acacia mangium établi depuis 2006 à Ibi sur le plateau des Batéké en République Démocratique du Congo. Son objectif est d’évaluer, au bout de 7 ans, les provenances pour la croissance en hauteur et en diamètre et pour la biomasse et les stocks de carbone ainsi que les teneurs en carbone et azote dans les sols sous les provenances d’Acacia mangium comparativement à des sols de savane sans Acacia. Les résultats obtenus par cette étude ont permis de ressortir les différences entre provenances pour chacun des paramètres évalués. Les provenances de Papouasie-Nouvelle-Guinée ainsi que celles de Queensland (Australie) suivies des provenances de Malaisie, de Vietnam, de Chine, de Fidji et de Philippines se sont révélées être les meilleures pour les paramètres évalués au cours de cette étude. / This study is about evaluation of 46 provenances trial of Acacia mangium established since 2006 in Ibi on the Batéké plateau in the Democratic Republic of Congo. Its objective is to estimate, after 7 years, the best provenances for the growth in height and the diameter and for the biomass and the stocks of carbon as well as the contents in carbon and nitrogen in soils under Acacia mangium provenances compared with savanna soils without Acacia. The provenances from Papua New Guinea as well as those from Queensland (Australia) followed by provenances from Malaysia, Vietnam, China, Fiji and the Philippines showed to be the best for all studied parameters.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis explores how human dictated methods of introduction and species-specific traits interact to define spatial patterns in invasive plant populations using Acacia elata as a model species. I initially asked whether the relatively small invasive extent (when compared to congeners introduced for forestry or dune stabilization) of a species used widely for ornamental purposes (A. elata) is due to low rates of reproduction in South Africa. Results indicate that A. elata has similar traits to other invasive Australia Acacia species: annual seed input into the leaf litter was high (up to 5000 seeds m-2); large seedbanks develop (>20 000 seeds m-2) in established stands; seed germinability is very high (>90%); seeds accumulate mostly in the top soil layers but can infiltrate to depths of 40cm; and seed germination appears to be stimulated by fire. I argue that the current limited distribution of invasive A. elata populations is not attributable to species-specific reproductive traits. Following on from this I addressed the relative importance of species traits, the recipient environment, and introduction dynamics using species distribution models and spread models defined using a range of parameters representative of invasive Australian acacia species. Results indicate that in the early stages of simulated invasions, the number of trees introduced was the most important parameter influencing abundance and extent, while the placement of introduction foci in urban areas associated with ornamental introductions limited the extent and abundance of invasive populations. I suggest that conditions relating to human-mediated introduction events initially mask the influence of intrinsic species traits and help to explain the failure and success of species associated with specific human-shaped pathways. Third, I used scale-area curves to determine how these human-dictated introduction conditions influenced the spatial structure of populations. The fractal dimension (Dij) of A. elata populations indicates plot scale (2.5-25m) spread with high densities that are increasing. Artefacts of introduction history were observed at the regional scale (2.5-25km) - populations are contiguous around introduction foci such as towns and roads. Moreover, fragmentation of A. elata populations at local to landscape scales (0.25-2.5km) is due to a combination of the haphazard regional placement and limited secondary dispersal vectors, both of which can be linked to their introduction history. In summary, this study used a combination of field-based data, modelling techniques and broad-scale sampling methods to assess how intrinsic species traits and introduction conditions mediate invasive spread. I conclude that introduction history can have a long-lasting (100+ years) influence on the spatial structure and distribution of invasive plants, which can mask the influence of individual species traits. / AFRIKAANSE OPSOMMING: Alhoewel menigte plant spesies deur mense ingevoer word, word slegs 'n klein hoeveelheid van plante indringers. Die beperkte aantal spesies wat in nuwe habitatte vestig en versprei, kan grotendeels toegeskryf word aan die omgewing en mensgemaakte hindernisse ten opsigte van oorlewing, voortplanting en verspreiding. In hierdie tesis gebruik ek Acacia elata as ʼn model spesie om te ondersoek hoe die invoeringsproses sowel as spesie spesifieke eienskappe die ruimtelike struktuur van indringende populasies bepaal. Aanvanklik was my vraag of die relatiewe klein indringingsarea van ʼn spesie wat ingevoer is vir ornamentele doeleindes (Acacia elata), teenoor die groot indringingsareas van Australiese Acacia-spesies wat ingevoer is vir bosbou of duin stabilisering, die gevolg is van lae voortplantings tempo in Suid-Afrika. Resultate dui daarop dat A. elata soortgelyke eienskappe as ander indringende Australië akasia spesies het: jaarlikse saad produksie is hoog (tot 5000 sade m - 2); groot ontwikkelde saadbanke (> 20 000 sade m - 2); hoë saad ontkieming (> 90 %); saad versamel in die boonste grondlae, alhoewel dit kan infiltreer tot 'n diepte van 40 cm; laastens, ontkieming word deur vuur gestimuleer. Hierdie resultate stel voor dat die huidige beperkte verspreiding van indringende A. elata populasies nie die gevolg is van spesie spesifieke voortplantings eienskappe nie. Gevolglik het ek 11 indringende Australiese akasia-spesies ondersoek om die relatiewe belangrikheid van spesie eienskappe, die area waar hul geplant is, asook invoerings aspekte te ondersoek. Resultate wys dat die aantal bome wat ingevoer is, die belangrikste eienskap was ten opsigte van digtheid en verspreiding van ʼn indringende spesie, terwyl invoering naby fokuspunte in stedelike gebiede weer spesie digtheid en verspreiding beperk. Hierdie resultate toon dat spesies eienskappe aanvanklik nie ʼn groot invloed het op hul sukses nie, maar dat hul sukses eerder afhang van waar hul geplant word. Derdens, gebruik ek skaal - area kurwes om te bepaal hoe die invoering van A. elata die ruimtelike struktuur van populasies beïnvloed het. Die fraktale dimensie (Dij) van A. elata bevolkings dui op verspreiding by die plaaslike vlak (2,5 - 25m), wat voorstel dat verspreiding nie op hierdie skaal beperk is nie. Eienskappe van die rede/metode van invoering was wel waargeneem op die groter skaal (2.5 - 25km) waar populasies digter was naby dorpe en paaie. Die intermediêre skaal (0,25 - 2.5km) dui daarop dat A. elata populasies huidiglik beperk word deur 'n kombinasie van lukrake plasing en beperkte sekondêre verspreiding, albei wat gekoppel kan word aan hul invoer geskiedenis. Hierdie studie maak dus gebruik van 'n kombinasie van veld gebaseerde data, modellerings tegnieke en breë skaal steekproefmetodes om te evalueer hoe algemene spesies eienskappe en invoer toestande verspreiding bepaal. Sodoende verskaf ek ʼn raamwerk om die invloed van invoer toestande op die ruimtelike struktuur en verspreiding van ornamentele plant indringers te verstaan.

O gênero Acacia apresenta espécies florestais de rápido crescimento, com rotações curtas (7 a 9 anos) e de grande interesse comercial para produção de polpa celulósica, painéis de madeira e energia. No Brasil a utilização de espécies do gênero Acacia na produção de celulose de fibra curta ainda é bastante restrita e são poucos os estudos que demonstram a potencialidade do uso dessa matéria-prima para a obtenção de polpa celulósica com as propriedades alcançadas pelas espécies do gênero Eucalyptus. Este trabalho teve como objetivo analisar o potencial de algumas espécies do gênero Acacia (A.aulacocarpa, A. auriculiformis, A. crassicarpa, A. mangium) plantados no Brasil, para a produção de polpa celulósica Kraft, considerando os aspectos relacionados à qualidade da madeira e da polpa, o consumo de reagentes químicos na polpação e também os aspectos relacionados ao rendimento e a capacidade de produção de polpa celulósica; adicionalmente buscou-se fornecer informações estratégicas para o setor celulósico nacional com relação as possíveis ameaças e as oportunidades apresentadas pelos materiais não utilizados no Brasil. Para realização deste trabalho foram utilizados 11 materiais genéticos distintos e cada um dos materiais genéticos foi considerado um tratamento e todos com 5 anos de idade. As características avaliadas foram: densidade básica, dimensões das fibras, composição química e parâmetros da polpação kraft (rendimento bruto, rendimento depurado, teor de rejeitos, número kappa e relações). Para este último objetivo, as madeiras de cada uma das espécies foram submetidas ao processo de polpação kraft, considerando-se seis níveis de álcali ativo: 18,0; 19,5; 21,0; 22,5; 24,0 e 25,5%, mantendo-se constantes as outras variáveis de cozimento. Observou-se que o modelo de variação longitudinal para densidade básica da árvore mantém uma tendência dos valores serem mais elevados na base e valores mínimos entre 25 e 50% da altura comercial. Quanto à composição química os valores foram distintos para todas as espécies e apresentaram uma variação de 60,99% para A. auriculiformis (1) e 68,79% para A. aulacocarpa (1) como valores mínimo e máximo. Os resultados obtidos quanto às dimensões das fibras não apresentaram padrões definidos de variação entre as espécies. Notou-se quanto aos parâmetros da polpação um efeito diferenciado entre as espécies de Acacia para as distintas cargas de álcali ativo. Considerando a curva de polpação para obtenção de número kappa 18 entre as espécies estudadas, obteve-se como média para a demanda carga de alcalina 23,8% e a média do rendimento depurado nestas condições foi 54,72%. A espécie A. crassicarpa procedência (1) destacou-se por apresentar a maior conversão em massa (ton/ha) de madeira na produção de celulose e a A. mangium procedências (1, 2, 3 e principalmente 4) alcançaram os melhores resultados de rendimento frente ao processo kraft de polpação comparando toas as espécies deste estudo. / The genus Acacia includes fast-growing short-rotation (7 to 9 years) forest tree species of commercial interest to produce pulp, wood panels, and energy. In Brazil, the utilization of species of the genus Acacia to produce short fiber pulp is still highly restricted and few studies are available that demonstrate the potential use of this raw material to obtain pulp presenting the properties displayed by species of the genus Eucalyptus. This study aimed at analyzing the potential of some species of the genus Acacia (A. aulacocarpa, A. auriculiformis, A. crassicarpa, A. mangium) planted in Brazil to produce kraft pulp, considering the aspects related to wood and pulp quality, consumption of chemical reagents during the pulping process, yield, and cellulose pulp production capacity. Furthermore, this work searched for strategical information for the national pulp and paper sector as to possible threats and opportunities presented by materials not used in Brazil in order to provide knowledge and discuss the potential competitiveness of these types of wood in the world market for pulp and paper. To accomplish these goals, we used 11 5-year-old distinct genetic materials, each one of them considered a different treatment. The following traits were evaluated: basic density, longitudinal variation, fiber dimensions, chemical composition, and kraft pulping process parameters (total yield, screened yield, rejects content, kappa number and relations). To carry out these evaluations, each wood species underwent the kraft pulping process considering six levels of active alkalis: 18.0, 19.5, 21.0, 22.5, 24.0, and 25.5%, keeping all other cooking variables constant. We observed that the model of longitudinal variation in the basic density maintains the trend of reaching higher values in the base of the tree and minimum values between 25% and 50% of the commercial height. The values found for the chemical composition were different for all the species studied and the holocellulose content ranged from a minimum of 60.99% found for A. auriculiformis (1) to a maximum of 68.79% found for A. aulacocarpa (1). The results obtained for fiber dimensions did not present defined patterns of variation among the species. The kraft pulping process parameters showed differences among Acacia species for the distinct levels of active alkalis. Considering the pulping process curve to get the kappa number of 18 among the species studied, the average alkali demand was 23.8% and the average depurated yield under these conditions was 54.72%. A. crassicarpa procedure 1 presented the highest conversion into wood mass (t/ha) to produce cellulose and A. mangium procedures (1, 2, 3, and mainly 4) reached the best results in terms of yield when they underwent the kraft pulping process compared to all the species studied herein.

O gênero Acacia apresenta espécies florestais de rápido crescimento, com rotações curtas (7 a 9 anos) e de grande interesse comercial para produção de polpa celulósica, painéis de madeira e energia. No Brasil a utilização de espécies do gênero Acacia na produção de celulose de fibra curta ainda é bastante restrita e são poucos os estudos que demonstram a potencialidade do uso dessa matéria-prima para a obtenção de polpa celulósica com as propriedades alcançadas pelas espécies do gênero Eucalyptus. Este trabalho teve como objetivo analisar o potencial de algumas espécies do gênero Acacia (A.aulacocarpa, A. auriculiformis, A. crassicarpa, A. mangium) plantados no Brasil, para a produção de polpa celulósica Kraft, considerando os aspectos relacionados à qualidade da madeira e da polpa, o consumo de reagentes químicos na polpação e também os aspectos relacionados ao rendimento e a capacidade de produção de polpa celulósica; adicionalmente buscou-se fornecer informações estratégicas para o setor celulósico nacional com relação as possíveis ameaças e as oportunidades apresentadas pelos materiais não utilizados no Brasil. Para realização deste trabalho foram utilizados 11 materiais genéticos distintos e cada um dos materiais genéticos foi considerado um tratamento e todos com 5 anos de idade. As características avaliadas foram: densidade básica, dimensões das fibras, composição química e parâmetros da polpação kraft (rendimento bruto, rendimento depurado, teor de rejeitos, número kappa e relações). Para este último objetivo, as madeiras de cada uma das espécies foram submetidas ao processo de polpação kraft, considerando-se seis níveis de álcali ativo: 18,0; 19,5; 21,0; 22,5; 24,0 e 25,5%, mantendo-se constantes as outras variáveis de cozimento. Observou-se que o modelo de variação longitudinal para densidade básica da árvore mantém uma tendência dos valores serem mais elevados na base e valores mínimos entre 25 e 50% da altura comercial. Quanto à composição química os valores foram distintos para todas as espécies e apresentaram uma variação de 60,99% para A. auriculiformis (1) e 68,79% para A. aulacocarpa (1) como valores mínimo e máximo. Os resultados obtidos quanto às dimensões das fibras não apresentaram padrões definidos de variação entre as espécies. Notou-se quanto aos parâmetros da polpação um efeito diferenciado entre as espécies de Acacia para as distintas cargas de álcali ativo. Considerando a curva de polpação para obtenção de número kappa 18 entre as espécies estudadas, obteve-se como média para a demanda carga de alcalina 23,8% e a média do rendimento depurado nestas condições foi 54,72%. A espécie A. crassicarpa procedência (1) destacou-se por apresentar a maior conversão em massa (ton/ha) de madeira na produção de celulose e a A. mangium procedências (1, 2, 3 e principalmente 4) alcançaram os melhores resultados de rendimento frente ao processo kraft de polpação comparando toas as espécies deste estudo. / The genus Acacia includes fast-growing short-rotation (7 to 9 years) forest tree species of commercial interest to produce pulp, wood panels, and energy. In Brazil, the utilization of species of the genus Acacia to produce short fiber pulp is still highly restricted and few studies are available that demonstrate the potential use of this raw material to obtain pulp presenting the properties displayed by species of the genus Eucalyptus. This study aimed at analyzing the potential of some species of the genus Acacia (A. aulacocarpa, A. auriculiformis, A. crassicarpa, A. mangium) planted in Brazil to produce kraft pulp, considering the aspects related to wood and pulp quality, consumption of chemical reagents during the pulping process, yield, and cellulose pulp production capacity. Furthermore, this work searched for strategical information for the national pulp and paper sector as to possible threats and opportunities presented by materials not used in Brazil in order to provide knowledge and discuss the potential competitiveness of these types of wood in the world market for pulp and paper. To accomplish these goals, we used 11 5-year-old distinct genetic materials, each one of them considered a different treatment. The following traits were evaluated: basic density, longitudinal variation, fiber dimensions, chemical composition, and kraft pulping process parameters (total yield, screened yield, rejects content, kappa number and relations). To carry out these evaluations, each wood species underwent the kraft pulping process considering six levels of active alkalis: 18.0, 19.5, 21.0, 22.5, 24.0, and 25.5%, keeping all other cooking variables constant. We observed that the model of longitudinal variation in the basic density maintains the trend of reaching higher values in the base of the tree and minimum values between 25% and 50% of the commercial height. The values found for the chemical composition were different for all the species studied and the holocellulose content ranged from a minimum of 60.99% found for A. auriculiformis (1) to a maximum of 68.79% found for A. aulacocarpa (1). The results obtained for fiber dimensions did not present defined patterns of variation among the species. The kraft pulping process parameters showed differences among Acacia species for the distinct levels of active alkalis. Considering the pulping process curve to get the kappa number of 18 among the species studied, the average alkali demand was 23.8% and the average depurated yield under these conditions was 54.72%. A. crassicarpa procedure 1 presented the highest conversion into wood mass (t/ha) to produce cellulose and A. mangium procedures (1, 2, 3, and mainly 4) reached the best results in terms of yield when they underwent the kraft pulping process compared to all the species studied herein.

Bibliography: leaves 227-244. This study is conceived to address various aspects of western myall (Acacia papyrocarpa Benth) recruitment, lifespan, distribution and the effects of major vertebrates on the species' ecology over the major part of its range in South Australia. A study of the population dynamics of the species is done to assess the adequacy of net recruitment. Population structure is examined across the woodlands. The new concept of "fossil paddocks" is adopted to investigate the historical impact of introduced herbivores on the landscape.